This invention relates to a multichannel radio communication system for selectively signaling energy management terminals at electric power user locations. More particularly, the invention relates to a radio communication system for electric utility automated distribution networks wherein plural multipurpose, multitone signals are transmitted in different signaling channels of one or more auxiliary channels of a composite commercial broadcast channel concurrently transmitting broadcast station programming in a main channel.
Various communication systems have been proposed for remotely monitoring and controlling the use of electric energy supplied to large numbers of customer locations. Large numbers of geographically dispersed residential electric power customers are supplied electric energy by distribution networks. It is often desired to control and monitor, from a central control station, the levels of electric energy supplied by the distribution network.
One system for a remotely controlled or automated distribution system (ADS) is disclosed in U.S. Pat. No. 3,911,415, assigned to the assignee of this invention, wherein bidirectional carrier communication signals are transmitted over power line conductors between a central station and each of large numbers of electric power customers. U.S. Pat. No. 3,659,280 discloses a power line carrier communication system wherein plural transmitters and receivers are operated at different selective frequencies of signals transmitted over the power lines. The present invention is more closely related to and is an improvement of U.S. Pat. No. 3,980,954, assigned to the assignee of this invention, disclosing and claiming a bidirectional communication system for ADS control, utilizing a VHF-FM broadcast transmitter signal which is modulated with interrogation or command signals transmitted to radio receivers at each customer location. Response signals from the customer locations are transmitted by carrier signals applied through the power lines, as disclosed in the aforementioned U.S. Pat. No. 3,911,415.
In U.S. Pat. No. 3,815,119 a remote meter reading system is described utilizing electric power lines and a mobile radio interrogating arrangement. A plurality of meters have separate transmitters for transmitting meter data at different frequencies to receivers mounted on utility poles and connected to the power lines to receive the transmitter signals. The receiver signals are coupled to a transponder which includes a radio transmitter. Transmitted radio signals are produced including serial transmissions of the meter readings of each separate meter.
In U.S. Pat. No. 3,705,385 and British Patent Specification No. 1,400,477, published July 16, 1975, there are described remote meter reading systems utilizing RF communication links for readout of meter reading data. In U.S. Pat. No. 3,919,640, a remote meter reading system includes an RF radio communication link. Digital and analog data signals are transmitted on different frequency channels through the radio link. The receiving station includes plural bandpass filters and frequency detecting circuits to separately detect the data transmitted at different frequencies from the remote meter reading location. In U.S. Pat. No. 3,656,112, a remote utility meter reading system includes a communication system which produces carrier signals over the power line and also a radio link. A general addressing technique is utilized in each of the aforementioned systems wherein each remote location includes a unique binary coded address and the communication signals are transmitted in a serial fashion with each remote location being signaled or responding in a sequential manner with the associated location being designated by a unique code. Accordingly, complex and complicated address responsive circuitry is required in each of the communication terminals for handling separate communications to separate customer locations.
A very practical limitation exists for general radio control and monitoring systems in that governmental approval for allocation of frequencies is difficult to obtain. The existing radio frequencies are already allocated and widely used so that new uses for the frequencies will conflict and interfere with the existing frequency users.
The U.S. Pat. Nos. 3,534,266; 3,714,375 and 4,048,619 disclose radio communication systems, in addition to the aforementioned U.S. Pat. No. 3,980,954, wherein data signals are transmitted from a broadcast station transmitter in addition to the normal broadcast program information. The transmitted data is not disclosed for communicating selective address and control information to large numbers of remote locations receiving a quantity to be controlled and monitored by such information signals.